Induction by Electric Currents of Ethylene Biosynthesis in Cucumber (Cucumis sativus L.) Fruit

The effects of an electric current on ethylene biosynthesis were investigated in cucumber (Cucumis sativus L.) fruit that were producing almost no ethylene. Direct currents at 0.5 to 3.0 milliamperes induced much ethylene synthesis, with a rapid continuous increase in the rate, which reached a peak within 5 to 6 hours and then decreased. The rate of production was greater with a stronger current. Ethylene production was not observed after the use of a sine-wave alternating current (60 hertz) at 3 milliamperes, the magnitude at which a direct current had the greatest effect. The activity of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ethylene forming enzyme (EFE) increased before the rise in ethylene production. ACC synthase and EFE were activated sixfold and fourfold, respectively, by 2 hours. The concentration of ACC increased linearly up to 6 hours and then decreased. Ethylene induction by an electric current was suppressed almost completely by the infiltration of the cucumbers with 5 millimolar aminooxyacetic acid, an inhibitor of ACC synthase, and was also suppressed 70% by 5 millimolar salicylic acid, an inhibitor of EFE. The results indicate that the ethylene induced by the direct current was synthesized via the ACC-ethylene pathway as a result of electrical stress, a new kind of stress to be identified.     

松辽盆地阿尔必期微体浮游植物新属种

该文描述了松辽盆地中白垩世阿尔必期泉头组三段的微体浮游植物化石1新属7新种,隶属于微咸水沟鞭藻类2属5新种(含4新亚种),淡水绿藻1属1种和疑源类1新属1新种。并对沟鞭藻 Ngktericysta Bint,1986进行了修订。     

松辽盆地白垩纪微体浮游植物群及其环境讨论

该文报道了松辽盆地白垩纪丰富的非海相微体浮游植物群,主要是沟鞭藻类及一些绿藻和疑源类;论述了藻类的生物地层特征,自下而上初步划分出10个组合带;结合微量元素和古地磁等资料,较详细地讨论了含微体浮游植物组段的沉积环境,认为松辽盆地在白垩纪至少遭受过两次重要的海侵(分别在青山口组一段及嫩江组一、二段沉积时期),导致古松辽湖泊五种不同水体环境的演替,指出微体浮游植物组合的变化是受古盐度、古温度和古水深等因素控制的。此外,对有关组段的地质时代也进行了讨论,进一步补充了新的浮游植物化石证据。     

光合能量代谢对C_3植物光呼吸的调节作用

C_3植物光呼吸与光合作用关系受光合能量代谢状况的调节。在外界无CO_2和照光条件下,贮藏性光合产物经某种转化途径能“回迁”光合与光呼吸碳循环并显著地受到光合能量代谢的影响。在无CO_2或低CO_2浓度、高光强条件下,此碳素“回迁”过程对协调光合能量代谢与光合碳素代谢平衡,可能起重要作用。     

用三维图象量测卵裂前蛙卵膜分子的三维运动

两栖类卵第一次卵裂前,缩时电影显示出卵表面有收缩波。由于卵的体积未变,在收缩时卵的高度必然增加。Sawai(1978)利用棱镜侧面摄取了蝾螈卵轮廓的高度变化,证实了卵裂前卵最高处的高度确有增加。但这一方法不能测知整个卵表面各处的高度变化,而且仅是二维的。在林蛙卵上,我们用荧光漂白恢复技术发现第一次卵裂前卵表面分子有规律性的流动,推测这是卵球的张弛。为了进一步     

Characterization of the guinea pig cytomegalovirus genome by molecular cloning and physical mapping.

Fragments of guinea pig cytomegalovirus (GPCMV) DNA produced by HindIII or EcoRI restriction endonuclease digestion were cloned into vectors pBR322 and pACYC184, and recombinant fragments representing ca. 97% of the genome were constructed. Hybridization of 32P-labeled cloned and gel-purified HindIII, EcoRI, and XbaI fragments to Southern blots of HindIII-, EcoRI-, and XbaI-cleaved GPCMV DNA verified the viral origin of cloned fragments and allowed construction of HindIII, EcoRI, and XbaI restriction maps. On the basis of the cloning and mapping experiments, the size of GPCMV DNA was calculated to include 239 kilobase pairs, corresponding to a molecular weight of 158 X 10(6). No cross-hybridization between any internal fragments was seen. We conclude that the GPCMV genome consists of a long unique sequence with terminal repeat sequences but without internal repeat regions. In addition, GPCMV DNA molecules exist in two forms. In the predominant form, the molecules demonstrate sequence homology between the terminal fragments; in the minor population, one terminal fragment is smaller by 0.7 X 10(6) daltons and is not homologous with the fragment at the other end of the physical map. The structural organization of GPCMV DNA is unique for a herpesvirus DNA, similar in its simplicity to the structure reported for murine cytomegalovirus DNA and quite dissimilar from that of human cytomegalovirus DNA.     

水稻品种超氧物歧化酶(SOD)活性与氧抑光合的关系

O_2抑光合程度不同的水稻品种,SOD活性存在差异。在40％O_2下,SOD活性被诱导增加水平高、延续时间长的品种,表现O_2抑光合程度小,反之则O_2抑光合程度大。在自然条件下,强光、高温都是诱导SOD活性变化的因素。选择SOD活性高、O_2抑光合程度小的种质资源可能有利于适应对光合不利的逆境条件。